Effects Of Two Oxidative Cleaning Agents On The Performance And Properties Of Polymeric Ultrafiltration Membrane

Chemical cleaning is indispensable for the sustainable running of ultrafiltration systems.At present,the commonly used membrane cleaning agent is sodium hypochlorite?NaClO?.As a cleaning agent,NaClO will react with polymer membrane materials and additives while detaching contaminants from the membrane The chemical composition and physical and chemical properties of the membrane,which in turn affect the membrane's retention performance and its lifespan.Aiming at the above problems,In this paper,through simulated chemical cleaning experiments,the effects of NaClO cleaning conditions on the performance and characteristics of polyethersulfone?PES?membranes and polyvinylidene fluoride?PVDF?membranes were first investigated,and then the cleaning efficiency of organic pollution and the influence on membrane performance and characteristics by hydrogen peroxide?H2O2?were investigated.and its feasibility as a cleaning agent was evaluated.The main conclusions of the paper are as follows:?1?In terms of the effect of NaClO on the performance of PES and PVDF membranes,pH 3-11 NaClO solution reduced the retention capacity of PES membranes for organic matter,and the pure water flux increased significantly,of which the most obvious effect were under neutral and weak alkaline conditions;PVDF The resistance of the membrane to NaClO was significantly better than that of PES membrane,and the pH of NaClO solution had no significant effect on the change of pure water flux and retention capacity of PVDF membrane.?2?The analysis of the chemical composition and characteristics of the membrane surface showed that at the exposure dose(500 ghL^-1)investigated in this study,NaClO caused PES molecular chain breakage,especially under weak alkaline and neutral conditions;NaClO did not cause significant changes in PVDF molecular structure.For the additive polyvinylpyrrolidone?PVP?,NaClO almost completely oxidizes PVP under acidic conditions,but its oxidation products were not lost,while under neutral and weakly alkaline conditions,most of the oxidation products were lost from the membrane.?3?The cleaning experiments of ultrafiltration membranes?UF?contaminated with humic acid?HS?showed that the cleaning efficiency of H2O2 under strong alkaline condition was comparable to that of NaClO,but the cleaning efficiency of H2O2 at other pH was significantly lower than that of NaClO.The analysis of chargeability shows that NaClO can significantly change the properties of HS at pH 9 and 11,while H2O2 only causeed a significant change of the properties of HS at pH 11.?4?At the same exposure dose,the impact of H2O2 on the water permeability,retention capacity and antifouling performance of PES and PVDF membranes were significantly lower than that of NaClO;for PES and PVDF membranes,neither H2O2caused a change in the molecular chain structure of the membrane host material,but it resulted in a certain degree of oxidation of the additive PVP and partial loss of PVP from the membrane surface,which caused the membrane interface properties to change,and the change was significantly smaller than that caused by NaClO change.